Optical systems often comprise mechanically moved optical elements or assemblies of optical elements. These are typically zoom devices or focussing devices. At least one optical element is in this case guided along a predetermined path of movement between two end positions. For example, the movement of a first optical element may take place along an axis in a non-linear way, while the movement of the second optical element has a different movement sequence in relation to the position of the first optical element. A non-linear movement sequence of the optical elements often arises from the necessity of adapting the focal length and the depth of field of the optical system to an observing situation.
U.S. Pat. No. 4,391,496 discloses an adjusting device for a pancratic objective of a stereo microscope with two lens elements that are displaceable in relation to one another along the optical axis. The adjusting device has a first slide element for a first lens element and a second slide element for a second lens element. The slide element is referred to in this document as a support. The first slide element can be displaced by means of a handle. Arranged between the first slide element and the second slide element is a coupling element, which is referred to in the document as a hinge element. The coupling element is in engagement with a control cam. The coupling element consists of a toggle lever, which is respectively supported by one leg on one of the slide elements that are pretensioned against one another by spring force and is supported by its folding location on the fixed-in-place control cam by way of a wheel that is rotatable about a folding axis.
This device has the disadvantage that a number of components are necessary for the coupling element, to be specific two legs and a rotatable wheel. In particular in the case of very small optical systems, this involves increased production and assembly costs. Moreover, in certain positions great forces must be expected in the toggle lever and on the control cam. For example, to achieve a short distance between the two slide elements, a small enclosed angle is necessary at the folding location between the two legs. Since the folding location is supported on the control cam, this leads to great forces in this region, in particular to great forces within the two legs and on the bearing devices of the two legs. If the device is moved from one operating state into another operating state, this involves unfavorable force conditions of the forces that are transferred from the first slide element to the second slide element, since the transfer of the forces that act in the axial direction from the first slide element to the second slide element also takes place by way of the legs of the toggle lever. The unfavorable force conditions necessitate the use of a strong spring in order to connect the second slide element to the first slide element by way of the coupling element reliably and without play.